1. Field of the invention
The present invention relates to a scan-exposure apparatus. More particularly, the present invention relates to a scan-exposure apparatus that can render an exposure signal pattern similar to a modulation signal pattern when the intensity of an exposure beam is modulated based on the modulation signal.
2. Related art
In a scan-exposure apparatus that modulates output intensity, the influence of an intensity distribution pattern on the exposure beam needs to be reduced in order to generate an exposure beam having an exposure pattern that corresponds to a modulation signal pattern because the intensity distribution pattern of the exposure beam is not linear.
Conventionally, to attain this object, a hyper-elliptic exposure beam whose minor axis is parallel to the scanning direction has been employed. Alternatively, a high frequency clock signal for driving a modulation signal generation means has been used to eliminate the intensity distribution influence in advance.
However, employing a hyper-elliptic exposure beam requires higher precision of the optical parts of the scan exposure apparatus and raises the costs without sufficiently reducing the influence of the intensity distribution on the exposure beam.
On the other hand, the clock signal for driving a higher precision modulation signal generation means must be provided at a higher frequency. Thus, a faster semiconductor element used as the modulation signal generation means must be employed, which may be technically difficult and costly.